Early on we had some troubles with the BT modules but thought we had those corrected. Mind telling me what version of VAG-COM you are running?
How do I know about the troubles? We mod'd my '06 A4 to add the BT capability such that we could check it out and fix the problem. That was 2 years ago and as far as I know, we have not had trouble since.
It would be good for you to tell me what kind of interface you have, the version of VAG-COM you are running and so on. The more info you provide the more likely we will be able to assist. An auto-scan would also be helpful.